Particle cleavage and ductile crack growth in a two-phase composite on a microscale

Abstract Failure of many practically relevant particulate two-phase composites can typically be attributed to cleavage fracture of the brittle particles succeeded by ductile crack growth in the matrix. Statistical methods can be employed to predict inclusion fracture depending on the particle shapes and configurations. Cracks in the matrix often originate from damaged hard inclusions. On the microscopic level – i.e. a length scale in the order of a few microns – most matrix materials develop a plastic zone around the crack tip large enough that the concept of linear elastic fracture mechanics cannot be applied anymore. In this study a crack tip opening angle (CTOA) criterion is used to simulate the crack propagation in the soft phase. The calculations are carried out in two dimensions using the finite element method. The influence of the growing crack on the stress distribution and subsequently on the probability of fracture of a second inclusion adjacent to the broken particle is investigated. For a given set of material parameters the issue whether a propagating crack will eventually stop or entail cleavage of the neighboring inclusion will be addressed. The role of the width of the matrix bridge between differently shaped particles will be emphasized.